The knee is one of the strongest and most stable bones in the body. It is constantly used and supports much of our weight. Due to this, the knee is prone to damage. The knee is comprised of three bones, the femur, the tibia and patella. The patella is the knee cap. Muscles, tendons and ligaments connect the knee. The knee is a hinge joint, making it move in one direction. The articular cartilage connects the ends of the bones in the knee to help it move smoothly. In osteoarthritis, this cartilage is damaged. The layer might get worn out or injured too. This causes stiffness and pain in the knee. Non-surgical treatments and medication usually help in treating the pain. However, if it does not work, a knee replacement may be suggested. If the level of damage is severe, your doctor will recommend a total knee replacement.